Ground effect vehicle

ABSTRACT

A ground effect vehicle including inner and peripheral annular nozzles for directing jet streams downwardly and inwardly and beneath an annular downwardly facing lifting surface which is surrounded by an arcuate annular restoring surface that angles upwardly and outwardly therefrom. The peripheral nozzle includes a skirt cooperating with the restoring surface to normally direct the peripheral jet stream downwardly and inwardly along the restoring surface to separate therefrom at a normal separation point to continue downwardly and turn outwardly to cooperate with the inner jet stream to form a generally uniform plenum chamber for supporting the vehicle. The skirt means cooperates with the restoring surface to be responsive to one side of the vehicle being brought into closer proximity with the ground then the opposite side to cause the separation point of the peripheral jet to shift upwardly and outwardly on the restoring surface of the one side of the vehicle to thereby increase the area of the annular plenum chamber on the one side to thereby tend to raise such one side higher off the ground thus maintaining such vehicle in a generally horizontal attitude.

United States Patent [191 Walter 1 July 24, 1973 GROUND EFFECT VEHICLE [76] Inventor: William C. Walter, 3025 Via La Selva, Palos Verdes Estates, Calif.

22 Filed: Dec. 10,1971

21 Appl. No.: 206,758

Related [1.8. Application Data [63] Continuation-impart of Ser. No. 43,536, June 4, 1970,

Primary Examiner-Gerald M. Forlenza Assistant Examiner--George H. Libman Attorney-Vern Schooley et al.

3/1965 Eggington 180/118 571 ABSTRACT A ground effect vehicle including inner and peripheral annular nozzles for directing jet streams downwardly and inwardly and beneath an annular downwardly facing lifting surface which is surrounded by an arcuate annular restoring surface that angles upwardly and outwardly therefrom. The peripheral nozzle includes a skirt cooperating with the restoring surface to normally direct the peripheral jet stream downwardly and inwardly along the restoring surface to separate therefrom at a normal separation point to continue downwardly and turn outwardly to cooperate with the inner jet stream to form a generally uniform plenum chamber for supporting the vehicle. The skirt means cooperates with the restoring surface to be responsive to one side of the vehicle being brought into closer proximity with the ground then the opposite side to cause the separation point of the peripheral jet to shift upwardly and outwardly on the restoring surface of the one side of the vehicle to thereby increase the area of the annular plenum chamber on the one side to thereby tend to raise such one side higher off the ground thus maintaining such vehicle in a generally horizontal attitude.

13 Claims, 12 Drawing Figures Patented July 24, 1973 3,747,726

3 Sheets-Sheet 1 6&6)? 25 if 3? 6 152 9 mid Patented July 24, 1973 3,747,726

3 Sheets-Sheet 73 [LL/HM E 74 3 475 3 Patented July 24, 1973 3 Sheets-Sheet 5 away GROUND EFFECT VEHICLE CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. application Ser. No. 43,536, filed June 4, 1970, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present, invention relates generally to ground effect or air cushion vehicles and, more particularly, to a ground effect vehicle which is relatively stable while operating at relatively great heights.

2. Description of the Prior Art Ground effect vehicles have been proposed which include downwardly opening central jet nozzles that emit jet streams forming central support columns and other vehicles have been proposed which include downwardly opening peripheral nozzles that emit jet streams which form peripheral curtains for supporting the vehi-' cle. Both of these types of ground effect vehicles are relatively unstable when operating at heights above approximately lO percent of their diameters.

Other ground effect vehicles have been proposed which include concentric central and peripheral nozzles but such vehicles fail to provide an arcuate upwardly and outwardly angled restoring surface surrounding the lifting surface. Likewise, such vehicles fail to have a peripheral skirt extending therearound and cooperating therewith to automatically shift the separation point upon changes in attitude of the vehicle with respect to the ground to thereby provide for inherent stability.

SUMMARY OF THE INVENTION The ground effect vehicle of present invention is characterized by annular inner and peripheral jet nozzles which direct respective jet streams downwardly and inwardly beneath an annular downwardly facing lifting surface. The lifting surface turns upwardly and outwardly to form a surrounding arcuate restoring surface and the peripheral nozzle includes a skirt which cooperates with the restoring surface to normally direct the peripheral jet stream downwardly and inwardly and which is responsive to one side of the vehicle being brought into closer proximity with the ground then the opposite side to cause such separation point to move upwardly and outwardly along the restoring surface of such one side to thereby increase the area between the inner and peripheral jet streams on such one side to increase the lifting force on such one side and raise such one side with respect to the ground.

Ground effect vehicles, when operating sufficiently close to the ground to be effected thereby, develop lifting force over that normally provided from jet thrust. The increased lift experienced as a result of this ground effect for a particular vehicle is frequently termed augmentation." Accordingly, it is an object of the present invention to provide a ground effect vehicle of the type described which exhibits a relatively large augmentation up to heights approximating the physical diameter of the vehicle.

It is a further object of the present invention to provide a ground effect vehicle of the type described which tends to be self-stabilizing at all operating heights.

Another object of the present invention is to provide a ground effect vehicle of the type described which utilizes a principle known as the Coanda Effect to control the direction of jet exhaust from the nozzles.

A further object of the present invention is to provide a ground effect vehicle which has a relatively small diameter for operation over available rights-of-way such as highways or freeways, while having sufficient stability to enable the vehicle to operate at heights which will enable it to accommodate relatively tall obstructions thereby enabling it to operate over unprepared terrain.

A further object of the invention is to provide a ground effect vehicle of the type described which can negotiate relatively steep inclines.

A still further object of the present invention is to provide a ground effect vehicle of the type described which is inherently both statically and dynamically stable.

It is also an object of the present invention to provide a ground effect vehicle of the type described which de' velops restoring forces in the air cushion for counteracting upsetting forces in every degree of freedom.

These and other objects and the advantages of the present invention will become apparent from a consideration of the following detailed description when taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is aperspective view of a ground effect vehicle embodying the present invention;

FIG. 2 is a vertical sectional view taken along the line 2-2 of FIG. 1; t

FIG. 3 is an enlarged fragmentary vertical sectional view similar to FIG. 2;

FIG. 4 is a bottom plan view of the ground effect vehicle shown in FIG. 1;

FIG. 5 is a perspective view of a second embodiment of the ground effect vehicle of present invention;

FIG. 6 is a vertical sectional view of the ground effect vehicle shown in FIG. 5;

FIG. 7 is an enlarged fragmentary vertical sectional view similar to FIG. 6;

FIG. 8 is a diagrammatic view depicting operation of the ground effect vehicle shown in FIG. 1;

FIG. 9 is a cross sectional view of a third embodiment of the ground effect vehicle of present invention;

FIG. 10 is a horizontal sectional view, in reduced scale, taken along the line 10-10 of FIG. 9;

FIG. 11 is a partial vertical schematic view of the ground effect vehicle shown in FIG. 9; and

FIG. 12 is a schematic view, in reduced scale, depecting operation of the ground effect vehicle shown in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1, 2 and 9, the ground effect vehicle of present invention includes, generally, a body formed with a circular in plan view core 11 which is covered by an annular skin 15. The cover skin 15 is formed with a central opening defining a jet intake 21 and is spaced from the core 11 to form a flow path 23 extending radially outwardly from the intake 21 and turning downwardly at the periphery of the core 11. A dividing ring 22 is interposed in the passage 23 between the periphery of the core 11 and the skin 15 to divide such passage and cooperates with the skin 15 to form a peripheral jet nozzle 25 which directs a peripheral jet stream 27 downwardly and inwardly. The dividing ring 22 cooperates with the inner core 11 to form a central jet nozzle 35 which opens inwardly to direct an annular central jet stream 39 inwardly along the bottom surface of the central core 11 until it encounters opposing flow that causes it to turn downwardly and then curve outwardly to form a central air curtain which cooperates with the peripheral jet stream 27 to form an annularshaped plenum chamber 43 that acts upwardly on the vehicle throughout an annular downwardly facing lifting area 41. The dividing ring 22 is semi-circular in vertical cross section to form an upwardly and outwardly curved restoring surface 42 that surrounds the lifting surface 41. In FIG. 8 the ground effect vehicle is shown in its normal operating condition disposed horizontally to the ground 47 shown in broken lines, and is also shown in solid lines after a downwardly acting unstabilizing force 48 has been applied to one side thereof. Similarly, in FIG. 11, the vehicle is shown traveling horizontally along horizontal ground 45, shown in broken lines, as it approaches an incline 46 shown in solid lines. It is noted that when the ground effect vehicle is operating horizontal to the ground, the peripheral skirt 65 formed by the cover skin cooperates with the restoring surface 42 to cause the peripheral jet stream 27 to separate from the restoring surface 42 at corresponding peripheral separation points 44 (FIG. 11) throughout the entire periphery of the vehicle. This causes the center of pressure of the plenum chamber 43 to be at 50 and 52 (FIG. 8) at the left and right side, respectively, of the vehicle. When the unstabilizing force 48 (FIG. 8) is applied to the front of the vehicle, or the vehicle encounters a hill 46 (FIG. 9), the front or left side of the vehicle will move downwardly with respect to the ground 45 (FIG. 8) or 46 (FIG. 9) thereby causing the separation points on such left side of the vehicle to shift upwardly and outwardly along the restoring surface 42 to 44' thus shifting the left hand center of pressure leftward from the point 50 to the point 51. Likewise, the separation points 44 on the right side of the vehicle will shift downwardly and inwardly on the restoring surface 42 thus serving to shift the center pressure of the plenum chamber 43 on the right hand side of the vehicle leftward from the point 52 to 54. As a result of the peripheral jet stream 27 on the left side of the vehicle moving a substantial distance leftward with respect to the underside of such vehicle, the plenum chamber 43 formed between the streams 27 and 39 will be substantially increased in horizontal cross sectional area thereby substantially increasing the lifting force under the left side of such vehicle. This modification in plenum chamber shape is depicted by the solid line outline shown in FIG. 12.

Referring to FIG. 2, the central core 11 is formed with a central inverted cone 57, the upper tip of which is in the form ofa rotatable hub 58 that carries a jet impeller 60 for driving air through the radially extending passage 23. The outer portion of the core 11 is in the form of an enlarged rim 59 which cooperates with the divider ring 22 to define an annular passage 61 leading to the central jet outlet 35.

A method frequently used for controlling the direction of exhaust from a jet is commonly referred to as the Coanda Effect or principle. This effect utilizes the physical principle that a jet stream can be caused to follow a curved path defined by one wall by merely moving a second wall sufficiently close to the first wall to reduce the thickness of flow passage defined between such walls below a critical thickness. When the flow passage is reduced below this critical thickness, the jet stream will be induced to follow the general curvature of the curved wall. This principle is utilized in both the peripheral nozzle 25 and the central nozzle 35. In this regard, the divider ring 22 is disposed sufficiently close to the periphery of the rim 59 of the central core 11 to reduce the thickness of the passage 61 below the critical thickness for the flow therethrough to thereby cause a jet stream 39 emitting from the nozzle 35 to follow the horizontal underside of the core 11 until it encounters the increased pressure under the vehicle thereby causing it to turn downwardly and eventually turn outwardly on itself.

Similarly, the Coanda Effect is utilized for directing flow from the peripheral nozzle 25. The downwardly turned peripheral portion of the skin 15 forms a cowling 65 which is disposed sufficiently close to the divider plate 22 to reduce the flow passage 67 defined therebetween below the critical thickness for the flow stream therethrough to cause the peripheral jet stream 27 emitted from the nozzle 25 to follow the contour of the divider plate 22 for a sufficient distance. This causes such jet stream to assume a 45 angle with the horizontal. While it is believed that this 45 angle for the peripheral jet stream is optimum, the peripheral jet may be directed at different angles which would perform satisfactorily.

During operation the impeller 60 will drive air through the radially outwardly directed passage 23 at relatively high velocities and such air will bedivided between the respective peripheral and central jet passages 67 and 61 to be emitted out the respective peripheral and central jet nozzles 25 and 35. The jet stream 27 will be emitted from the peripheral jet nozzle 25 at approximately 45 to the horizontal and will continue downwardly until it encounters sufficient pressure built up within the plenum chamber 43 to cause it to turn outwardly and while it continues its downward flow. Likewise, the jet stream 39 emitted from the central jet nozzle 35 will travel inwardly across the horizontal underside of the core 11 until it encounters sufficient pressure to cause it to turn downwardly and eventually be turned outwardly. The resulting central air curtain 39 acts as a barrier to air flow thereacross and will form a central air chamber 71 which will cooperate with the annular plenum chamber 43 to form a composite air cushion for supporting the ground effect vehicle.

Referring to FIG. 8, it will be noted that the plenum chamber 43 is essentially in the form of an outwardly facing quarter moon revolved through 360 and that the radii of curvature of the respective curtains 27 and 39 remain constant throughout the 360' revolution while such curtains remain undisturbed and the vehicle is maintained horizontal to the ground 47 as shown in broken lines.

However, when one side of the vehicle is lowered with respect to the ground, as by the unstabilizing force 48 (FIG. 8) acting downwardly on the left hand side thereof or the vehicle encountering an incline 46 (FIG. 1 l the downwardly and inwardly directed air curtains 27 and 39 on the lower side of such vehicle experience the ground effects and encounter higher pressures under the central portion of the vehicle sooner after they exit the respective jet nozzles 25 and 35 (FIG. 2) thereby causing them to turn outwardly sooner. Thus, the separation point from the restoring surface 42 on the lower side of such vehicle shifts upwardly and outwardly from the separation point 44 to the point 44' while the separation point on the opposite side of such vehicle shifts downwardly and inwardly a corresponding distance. Referring to FIG. 12, the resultant force distribution change on the lifting area 41 is represented by the difference between the uniform annular chamber 43 shown in broken lines in FIG. 12 and the eccentric annular chamber 43 shown in solid lines, it being realized that the larger area on the left hand side of the annular chamber 43 provides a larger lifting force under the left hand side of the annular lifting surface 41 of the vehicle to thereby raise such left hand side to a greater elevation from the ground 47 or 46. It will be appreciated that the larger the force 48, the greater will be the vehicle disturbance and consequent enlargement of the left side of the plenum chamber 43 to thereby provide an inherent stabilizing feature.

A ground effect vehicle similar to that shown in FIG. 1 is shown in FIGS. 5 7 and includes the central core 11 which cooperates with the outer skin to define a radially outwardly extending passage 23 on which is divided in two passages 67 and 61 leading to the respective peripheral and central jet nozzles 25 and 35. However, the outer passage 67 has a divider ring 81 disposed therein for dividing such passage into a passage 83 leading to the peripheral nozzle 25 and an intermediate passage 85 which directs a selected amount of air 87 inwardly to the plenum chamber 43 formed between the outer peripheral air curtain 27 and the inner annular air curtain 39. Referring to FIG. 7, a plurality of spaced apart directional vanes 91 are disposed in the passage 83 and are carried on pivot pins 93 leading to an electrical control units mounted in the core 11 whereby angularity of the directional blades 91 may be varied to impart torque to the body of the vehicle from the thrust exiting the peripheral jet nozzle 25.

Still referring to FIG. 7, spaced below the bottom edge of the cowling 65 are a plurality of strips of ring segments which form Coanda Trippers 95 which are carried from control rods 97 extending into the core 11 and driven inwardly and outwardly by control motors (not shown).

Spaced outwardly from the cowling 65 is an airfoil ring 101 which forms a funnel 103 for drawing air into the peripheral air curtain 27.

Referring to FIG. 6, the central core 11 is formed with an annular centrally disposed pressurizing passage 105 which leads downwardly from the impeller 60 to the central air chamber 71 for bleeding a controlled quantity of air into such chamber for appropriate pressurization thereof.

Operation of the ground effect vehicle shown is FIGS. 5 7 is similar to that described hereinabove with reference to the vehicle shown in FIG. 1 except that the divider ring 81 serves to bleed a controlled stream of air 87 into the plenum chamber 43 for effecting the desired pressurization thereof for the particular operating conditions. Likewise, the annular bleed passage I05 bleeds air into the central air chamber 71 at a rate sufficient to effect the desired pressurization thereof for the operating conditions.

Also, the directional vanes 91 (FIG. 7) may be inclined to direct the peripheral jet curtain 27 in a somewhat spiral fashion to counter the torque of the impeller and control the directional orientation of the ve hicle itself with respect to its vertical axis.

The airfoil ring 101 serves to draw additional air into the peripheral jet stream 27 as a consequence of the reduced pressure area immediately below the cowling as a result of the inward turning of the air stream 27.

The Coanda Tripper ring segments may be shifted inwardly and outwardly at selected locations around the periphery of the vehicle to control the angle at which the peripheral jet stream 27 is emitted. Since the Coanda Trippers 95 are spaced from the lower edge of the cowling 65 to provide for air flow therebetween, shifting with respect to the divider ring 81 will merely alter the direction of the jet stream 27 and will not upset the mass flow throughout the radially extending passage 23. It will be clear that the trippers 95 may be moved inwardly along one side, for example the front, of the vehicle to direct the peripheral jet curtain 27 on that one side more inwardly thereby causing the vehicle to tilt downwardly on that one side to angle the nozzles 25 and 35 somewhat rearwardly to provide a forward horizontal thrust component which will move the vehicle forwardly. A similar maneuver may be employed for climbing an incline.

The ground effect vehicle shown in FIGS. 9 11 is substantially the same as that shown in FIG. 1 except that the divider ring 22' is modified to project radially inwardly a greater distance under the vehicle to form the inner nozzle outlet 35 at a diameter equal to70.7 percent of the overall diameter to the outer periphery of such dividing ring 22. It has been determined both analytically and experimentally that this relative positioning of the nozzle 35 provides an optimum stand-off, or operating height, for the vehicle.

Additionally, the vehicle shown in FIGS. 9 and 10 includes a plurality of counter rotational vanes 121 arranged in a circular pattern and located in the outlet of the nozzle 35 to direct propulsive fluid moving therethrough in a spiral pattern 123 which causes the propulsive fluid emitted from the nozzle 35 on one side of the vehicle to spiral downwardly in the jet stream 39 to contact the ground 45 and emit from the jet stream 39 on the side opposite that of which it was expelled from the nozzle 35. The vanes 121 are arranged at a slight angle to the tangent of the circle defined by the nozzle outlet 35 to intercept the propulsive fluid and provide a counter rotational force on the vehicle which is balanced against the rotational force exerted on such vehicle by rotation of the impeller 60. Obviously, such vanes could be located in the peripheral nozzle 25 or arrays thereof could be arranged in both nozzles tobalance the dynamic forces on the vehicle as a result of both the rotation of the impeller 60 and momentum of the propulsive fluid on the vanes 121. It has been determined that the vanes 121 not only assist in balancing the forces created by rotation of the impeller 60, but the resultant spiral vortex developed in the jet stream 39 (FIG. 9) enhances the stability of the vehicle for greater stand-off heights.

As noted hereinabove, when the vehicle encounters an incline 46 (FIG. 11), the left extremity will automatically raise to rotate the vehicle about its center of gravity 127 until such vehicle assumes an attitude parallel with such incline.

From the foregoing detailed description, it will be apparent that the ground effect vehicle of present invention is relatively stable and develops restoring forces which tend to right the vehicle whenever it has been subjected to any unstabilizing force thereby enabling such vehicle to operate at greater heights than conventional vehicles. It is believed that ground effect vehicles constructed in accordance with the present invention will operate at heights of approximately 50 percent of their diameter as contrasted with the presently known vehicles which are unstable when operating at a height in excess of 10 percent or 20 percent of their diameter. Consequently, vehicles can be made with sufficiently small diameters to enable them to have access to areas that would otherwise be inaccessible and such vehicles can operate at a height which will enable them to negotiate over obstacles which would otherwise force selection of alternate routes.

Various modifications and changes may be made with regard to the foregoing detailed description without departing from the spirit of the invention.

1 claim:

1. A ground effect vehicle comprising:

a body formed with a downwardly facing lifting surface and a peripheral restoring surface extending around said lifting surface and angling upwardly and outwardly with respect thereto;

central jet means having a central nozzle opening within said lifting surface to direct a central jet stream downwardly relative to the interior of said lifting surface;

coanda nozzle means including peripheral skirt means surrounding said restoring surface and terminating in a lower edge spaced above the lower extremity of said angled restoring surface, said skirt means being spaced from said restoring surface a distance substantially no greater than the critical distance for a predetermined rate of flow of a selected propulsion fluid through said coanda nozzle means to normally direct a peripheral jet stream downwardly and inwardly relative to said body to encounter an interior pressure sufficient to cause it to bend outwardly thus causing it to separate from said restoring surface at normal separation points thereby forming an outer curtain cooperating with said central jet stream to form therebetween a peripheral plenum chamber below said lifting surface; and

drive means directing a central jet flow of said propulsion fluid to said central jet means and said predetermined rate of flow of said propulsion fluid to said coanda nozzle means.

2. A ground effect vehicle as set forth in claim 1 wherein:

said restoring surface and central nozzle are annular in horizontal cross section and said central nozzle has a diameter of substantially 70.7 percent of the maximum diameter of said restoring surface.

3. A ground effect vehicle as set forth in claim 1 that includes:

an airfoil surrounding said peripheral nozzle and formed to direct ambient air into the jet stream emitting therefrom. 4. A ground effect vehicle as set forth in claim 1 that includes:

means for controlling the direction at which said jet stream is emitted from one of said nozzles. 5. A ground effect vehicle as set forth in claim 1 wherein:

said body includes a central core and a skin covering the upper side of said core and formed centrally with a jet inlet, said skin being turned downwardly at the outer periphery of said core extremity terminating in its lower end at said edge, said skin cooperating with said core to define a jet passage leading from said peripheral inlet to said nozzle. 6. A ground effect vehicle as set forth in claim 1 wherein:

said central jet nozzle is directed inwardly toward the center of said central lifting surface to emit said jet stream directed substantially horizontally inwardly toward the center of said body. 7. A ground effect vehicle as set forth in claim 1 wherein:

said body includes a downwardly and inwardly curved partition which projects inwardly to form said lifting surface; and said skirt means is disposed in close spaced relationship with said partition. 8. A ground effect vehicle as set forth in claim 1 that includes:

vortex vanes disposed in one of said jet nozzles. 9. A ground effect vehicle as set forth in claim 1 wherein:

said drive means includes a horizontally disposed impeller for rotation in one direction and said vehicle includes: vanes disposed in one of said jet nozzles and angled to cooperate with said propulsive fluid to impart momentum to said vehicle in the rotary direction opposite said one direction. 10. A ground effect vehicle as set forth in claim 1 that includes:

vanes disposed in said central jet nozzle to impart a spiral flow pattern to said central jet stream to enhance the stability of said vehicle. 11. A ground effect vehicle as set forth in claim 1 wherein:

said restoring surface is curved upwardly and outwardly relative to said lifting surface. 12. A ground effect vehicle as set forth in claim 1 wherein:

said lifting surface, restoring surface, central nozzle and peripheral nozzle are circular in plan view. 13. A ground effect vehicle as set forth in claim 1 wherein:

said central nozzle includesa parametrically continuous outlet for emitting a parametrically continuous stream of said fluid to form a downwardly flowing parametrically continuous central curtain of said fluid.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3, 747,726 Dated July 24 l973 Inventor(s) William C. Walter- It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: Column 8, line 11, delete "extremity" and insert and Column 8, line 12, after "lower" insert extremity Column 8, line 14, after "said" (first occurrence) delete "peripheral" and after "said" (second occurrence) insert peripheral V p Column 8, line 18, after "said" (first occurrence) delete "central" and after "said" (second occurrence) insert central --.v I

Signed and sealed this 5th day of March 197A.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN I Attesting Officer Commissioner of Patents 'IORM po'wso USCOMM-DC eoan-Pw i U.5 GOVERNMENT PRINTING QFFIICE I") 0-3664. 

1. A ground effect vehicle comprising: a body formed with a downwardly facing lifting surface and a peripheral restoring surface extending around said lifting surface and angling upwardly and outwardly with respect thereto; central jet means having a central nozzle opening within said lifting surface to direct a central jet stream downwardly relative to the interior of said lifting surface; coanda nozzle means including peripheral skirt means surrounding said restoring surface and terminating in a lower edge spaced above the lower extremity of said angled restoring surface, said skirt means being spaced from said restoring surface a distance substantially no greater than the critical distance for a predeterMined rate of flow of a selected propulsion fluid through said coanda nozzle means to normally direct a peripheral jet stream downwardly and inwardly relative to said body to encounter an interior pressure sufficient to cause it to bend outwardly thus causing it to separate from said restoring surface at normal separation points thereby forming an outer curtain cooperating with said central jet stream to form therebetween a peripheral plenum chamber below said lifting surface; and drive means directing a central jet flow of said propulsion fluid to said central jet means and said predetermined rate of flow of said propulsion fluid to said coanda nozzle means.
 2. A ground effect vehicle as set forth in claim 1 wherein: said restoring surface and central nozzle are annular in horizontal cross section and said central nozzle has a diameter of substantially 70.7 percent of the maximum diameter of said restoring surface.
 3. A ground effect vehicle as set forth in claim 1 that includes: an airfoil surrounding said peripheral nozzle and formed to direct ambient air into the jet stream emitting therefrom.
 4. A ground effect vehicle as set forth in claim 1 that includes: means for controlling the direction at which said jet stream is emitted from one of said nozzles.
 5. A ground effect vehicle as set forth in claim 1 wherein: said body includes a central core and a skin covering the upper side of said core and formed centrally with a jet inlet, said skin being turned downwardly at the outer periphery of said core extremity terminating in its lower end at said edge, said skin cooperating with said core to define a jet passage leading from said peripheral inlet to said nozzle.
 6. A ground effect vehicle as set forth in claim 1 wherein: said central jet nozzle is directed inwardly toward the center of said central lifting surface to emit said jet stream directed substantially horizontally inwardly toward the center of said body.
 7. A ground effect vehicle as set forth in claim 1 wherein: said body includes a downwardly and inwardly curved partition which projects inwardly to form said lifting surface; and said skirt means is disposed in close spaced relationship with said partition.
 8. A ground effect vehicle as set forth in claim 1 that includes: vortex vanes disposed in one of said jet nozzles.
 9. A ground effect vehicle as set forth in claim 1 wherein: said drive means includes a horizontally disposed impeller for rotation in one direction and said vehicle includes: vanes disposed in one of said jet nozzles and angled to cooperate with said propulsive fluid to impart momentum to said vehicle in the rotary direction opposite said one direction.
 10. A ground effect vehicle as set forth in claim 1 that includes: vanes disposed in said central jet nozzle to impart a spiral flow pattern to said central jet stream to enhance the stability of said vehicle.
 11. A ground effect vehicle as set forth in claim 1 wherein: said restoring surface is curved upwardly and outwardly relative to said lifting surface.
 12. A ground effect vehicle as set forth in claim 1 wherein: said lifting surface, restoring surface, central nozzle and peripheral nozzle are circular in plan view.
 13. A ground effect vehicle as set forth in claim 1 wherein: said central nozzle includes a parametrically continuous outlet for emitting a parametrically continuous stream of said fluid to form a downwardly flowing parametrically continuous central curtain of said fluid. 